A gas turbine engine, typically used as a source of propulsion in aircraft, operates by drawing in ambient air, combusting that air with a fuel, and then forcing the exhaust from the combustion process out of the engine.
Typically, a gas turbine engine has a case surrounding the core components, such as a diffuser case surrounding a diffuser and combustor. An auxiliary gearbox is generally positioned near this diffuser case and in mechanical communication with the fan, compressor, and/or turbine. The combustor produces copious amounts of heat, some of which is transferred to the diffuser case and then transferred to the gearbox. Such heat can be detrimental to the operation and life of the gearbox. Specifically, the heat may cause any lubricant working in the gearbox to coke or components of the gearbox may be damaged due to heat stress.
In an effort to mitigate such heat related effects, cooling is typically provided to the auxiliary gearbox in the form of compressed air from the compressor, a fuel working as a coolant, or a dedicated coolant in addition to any cooling provided by a lubricant acting on the gearbox. While effective, such cooling requires extra components to communicate these fluids through the engine and, in the case of the dedicated coolant, may require additional equipment to remove heat from the coolant. These additional components and equipment increase the weight and size of the engine, as well as the maintenance needed to keep the engine operating.
Therefore, it can be seen that a need exists for a way to reduce the heat stress on the gearbox, while reducing the weight, size, and maintenance requirements of the engine.